calc how to edit email address in calc

OS X Version:
Build ID: 62ad5818884a2fc2e5780dd45466868d41009ec0

Want to edit some email addresses in cells in calc.
Cannot just edit the existing emailaddress, by typing in edit field in bar. because that will delete the existing email address.
Want to change abcd-efg@isl.rt into oooo-efg@isl.rt .
Do delete the abcd part, and type the oooo part.
Expect the email address in the field to be oooo-efg@isl.rt .
What happens in the field is only oooo .
How to edit the email-address?

I experienced the same problem, an this is quiet annoying.